Ukraine came from behind to beat South Korea 3-1 and win their first Under-20 World Cup.
The match - in Lodz, Poland - featured two teams playing in the final for the first time in their history.
South Korea led through an early penalty, which Lee Kang-in fired past Real Madrid goalkeeper Andriy Lunin.
But Vladyslav Supriaha scored either side of half-time and Dynamo Kiev club-mate Heorhii Tsitaishvili sped away to add a late third.
Korea almost equalised at 2-1 but 20-year-old Lunin, who spent last season on loan with Leganes in La Liga, brilliantly tipped Lee Jae-ik's header on to the crossbar.
Ukraine - who did not qualify in 2017 - topped a group containing the USA, Nigeria and Qatar, before beating Panama 4-1 in the last 16, Colombia 1-0 in the quarter-final and Italy 1-0 in the semis.
Norway's Erling Braut Haaland won the Golden Boot with nine goals, all in one game - a 12-0 group win over Honduras, his side's last game of the tournament.
Defending champions England failed to qualify for the finals.